1. Field of the Invention
The present invention relates to apparatus for giving instructions for the supply of parts from a parts supply factory to an assembly factory, hereinafter termed a "parts supply instruction apparatus".
2. Description of the Prior Art
There are three established systems used for the supply of parts from at least one parts supply factory to at least one assembly factory in the car manufacturing industry, namely, a "supply-on-schedule" system, a "supply-on-parts-consumption" system often called a "Kanban" system, and a "supply-in-order" system.
The "supply-on-schedule" system is a parts supply system according to which a parts supply schedule, including instructions relating to the type of part, the number of parts, a supply date, etc., is preliminarily made on the basis of a monthly car production schedule at the assembly factory. The parts supply schedule is given to the parts supply factory beforehand so that the parts can be manufactured well in advance, even though the actual parts supply is performed according to a fixed order which is given to the parts supply factory only a few days before the actual assembly operation utilizing the respective parts.
The "Kanban" system is a parts supply system according to which a parts supply order is made at the assembly factory on the basis of the actual consumption of parts thereat and is issued to the parts supply factory in the form of a card called a Kanban so that the same type and number of parts as are consumed, are supplied to the assembly factory "just in time" for their assembly into a car on the assembly line. The "Kanban" is conveyed back and forth between the parts supply factory and the assembly factory by a delivery truck together with a pallet for housing the respective parts.
The "supply-in-order" system is a parts supply system, according to which an order for the parts required for assembly into a respective car is issued by the assembly factory to the parts supply factory when the car is actually brought onto the assembly line so that the ordered parts are supplied to the assembly line before the car is conveyed to the respective positions on the assembly line where the parts are to be assembled into the car. In the "supply-in-order" system, the order in which the parts are supplied corresponds to the order in which cars are brought onto the assembly line, so that the order of supply of parts is thereby determined automatically.
Recently, a need has arisen to be able to select from a plurality of the above-described three parts supply systems so that production can be performed in the most effective manner. However, problems, as described below, have arisen in developing an apparatus capable of such a flexible selection.
Firstly, since the above-described three parts supply systems are independent of each other, a parts master file which records the parts specifications, control devices, e.g. sensing means, and an operating computer, dedicated for operating one system can not be used to operate any of the other systems.
Secondly, in order to change from one system to another system, the parts master file of the first system must be greatly changed in order to render it suitable for use in operating another one of the systems. Such a radical change will necessarily be accompanied by errors even if such modification is possible at all.
Thirdly, if each assembly factory were to be provided with all the different types of parts master files, sensors, and computers for the purpose of enabling changing-over between the systems, the cost increase would be unacceptably high.